Prior art round balers generally have a bale forming chamber defined by an apron comprising an array of side-by-side belts, transverse slats trained on chains, a plurality of rolls or a combination of these various elements, e.g., rolls and belts. Crop material, such as hay, is picked up from the ground, as the baler travels across the field, and is fed into a fixed or expandable chamber where it is rolled up to form a compact cylindrical ha package. While still inside the bale forming chamber in its compacted form, the outer surface of the package is wrapped with twine or web material, such as net, prior to ejecting the wrapped bale from the chamber onto the ground for subsequent handling.
Exemplary of prior art round balers of the general type mentioned above is the baler disclosed in U.S. Pat. No. 4,956,968 issued in the name of K. R. Underhill on Sep. 18, 1990. In this baler an apron consisting of a combination of rolls and belts is used for bale formation. The baler also includes a mechanism for supplying net to a dispensing assembly which in turn feeds the net material into the bale forming chamber for circumferentially wrapping a formed cylindrical package of crop material. The dispensing mechanism includes a net insertion arrangement having a grasping portion for pulling net from the supply mechanism and inserting the free edge, commonly referred to as the tail, into the chamber. Subsequent to wrapping, the net material is severed by a cutting device, comprising an assembly for thrusting a knife edge transversely through the path of the net while net tension is increased causing a severing action as the net is pulled against the knife edge.
In other round balers known in the art, various cutting devices are employed as exemplified by the apparatus disclosed in U.S. Pat. No. 4,597,241, issued Jul. 1, 1986, wherein a pair of opposing knives are used to shear the web material. In another known arrangement a knife strikes an anvil to provide the severing function as depicted in U.S. Pat. No. 4,922,690, issued May 8, 1990. Still another prior art mechanism contemplates a knife that is projected into a recess on the opposite side of the web path to urge the web against a cutting abutment, as shown in U.S. Pat. No. 4,599,844, issued Jul. 15, 1986.
Insofar a the severing element used in round balers is concerned, there are also different types used. In addition to the straight knife edge referred to above, other known means include a serrated edged knife as disclosed in U.S. Pat. No. 4,409,784, issued Oct. 18, 1983. Cutting devices in round balers wrapping systems have also been known to utilize a series of side-by-side triangular shaped knife elements projected into the path of the web material. This latter arrangement is embodied in the round baler apparatus disclosed in U.S. Pat. No. 4,604,855 and No. 4,407,113, issued Aug. 12, 1986, and Oct. 4, 1983, respectively.
The web wrapping material used in round balers is another factor having a bearing on the net severing assembly. Materials vary from a thin film of plastic to numerous types of net. One of the most commonly known net materials used in round balers is a woven fabric material, as shown by way of example in U.S. Pat. No. 4,569,439, issued Feb. 11, 1986 and No. 4,570,789, issued Feb. 18, 1986. A second equally as common net material used is made from extruded plastic, an example of which is disclosed in U.S. Pat. No. 4,781,291, issued Nov. 1, 1988.
During the general process of making a round bale, as discussed above, the package of hay becomes formed and wrapped by a continuous web of material while still in the bale forming chamber. At this stage in the process it is important that the severing of the net take place trouble free and that a substantially straight lateral edge is left on the end of the web that remains in the baler to enhance initiation of the next wrapping cycle. A straight lateral cut is also desirable from the standpoint of the bale that is being discharged to provide a snugly wrapped neat bale that facilitates handling. In the past, problems have been encountered when the woven net is improperly severed due to, e.g., bunching or sideways movement of the net at or prior to impact. Not only is the poor appearance and uneven end undesirable but a straggly end can be more readily snagged during processing of the next bale or handling of the discharged bale. Further, problems have arisen in attempts to provide a cutting means that is adaptable to effectively sever woven net as well as extruded net, both of which have different physical characteristics.